Farhad Kiani - Dept. of Mechanical Engineering, University of Yazd, Yazd, Iran
Mohammad Bozorg

This study is concerned with the computation of the robust performance domain of PID controllers in the plane of two coefficients (KP - KI). It deals with the computation of the admissible variations of PID controller coefficients using the H∞ results. The results are first applied to the plants with fixed transfer functions and a straight-forward method is presented for the computation of the permissible ranges of variations of the PID coefficients. Then, the method is extended to the cases where the plant itself has uncertain coefficients, and the properties of the Kharitonov polynomials are used to compute the admissible domains of the controller coefficients.

PID controller, Robust Performance, Kharitonov Theorem